Metal punch and die



Aug. 30, 1966 In 2/2222 for. f 3 film 0405 E/Yerrs fru m. i: J r h United States Patent 3,269,011 METAL PUNCH AND DIE Rudolph E. Herrstrum, Rockford, Ill., assignor to Greenlee Bros. & Co., a corporation of Illinois Filed Jan. 20, 1964, Ser. No. 338,806 2 Claims. (Cl. 30-360) This invention relates to metal punches and more particularly to a punch for forming square holes in sheet metal.

It is the general object of this invention to provide a new and improved square punch and die.

It is another object to provide such a new and improved punch and die of the draw type adapted for use in punching square holes in metal sheets, outlet boxes for electrical wiring, and other uses requiring a portable tool.

Other objects and advantages will appear from the description taken in connection with the accompanying drawings in which:

FIGURE 1 is a side elevational view of a square punch and die of the draw type embodying the invention.

FIGURE 2 is an end view looking at the right-hand end of FIGURE 1.

FIGURE 3 is an elevation looking at the left-hand end of FIGURE 1; and

FIGURE 4 is a section along the line 44 of FIG- URE 1.

As shown in the drawings, a preferred form of the invention comprises a die member 10, a die back-up member 11, a punch member 12, a draw rod 13 extend ing through a bore 14 in the punch member 12 and through a bore 15 in the back-up member 11. A nut 16 is screw threaded on the right-hand end 13 of the rod 13. Preferably, the left-hand end of the rod 13 is adapted to be connected to a suitable hydraulic ram R which exerts the necessary draw force on the rod 13 with respect to the die member and back-up member 11, so as to draw the punch member 12 toward the die member to form a hole in a sheet of metal M.

Preparatory to use of the punch and die in forming a square hole in the sheet M, a round hole M' is drilled in the sheet to permit the rod 13 to pass therethrough. The rod 13 has a keyway 13" extending longitudinally thereof into which keys 11' and 12' on the back-up member 11 and punch member 12, respectively, fit to prevent relative rotation between the parts 11, 12 and 13 and thereby insure alignment of the punch with the die.

In the form shown, the punch member 12 is of square cross section, being provided with four substantially fiat outer surfaces 17, suitably relieved, and the central portion 18 of the active face of the punch element is recessed so as to provide straight cutting edges 19 at the corners thereof and curved cutting edges 20 therebetween.

The die member 10 is provided with a square hole having side walls 21 extending therethrough. Centrally of each side wall an arcuate groove 22 extends from a point 23 adjacent the cutting edge 24 of the die member and to the rear surface of the die member. The rear surface of the die member is also provided with a pair of lugs 25 which interfit with corresponding recesses 26 in the back-up member 11 to prevent rotation between said two members. The back-up member is shown provided with a cylindrical boss 27 of a diameter fitting into the arcuate recesses 22 as shown best in FIGURE 4.

In producing a square punch and die of the draw type as shown in the drawings, the die member 10 may be formed from a piece of round bar steel stock which is 3 ,269 ,01 l Patented August 30, 1966 mounted in a lathe so as to permit first the. boring of a hole through the member of a diameter slightly less than the length of the side wall 21 of the square hole to be formed in the die member 10, this hole being drilled all the way through the die member. Thereafter, for example, while the member is still mounted in the lathe the relief grooves 22 are formed by a larger drill boring a hole which extends from the rear face of the die member only to the point 23. Thereafter, upon removing the die member from the lathe the square hole therein may be formed by a broaching operation which leaves the relief grooves 22 as shown.

The punch member 12 is preferably formed from square bar stock. Here, again, the cutting edges are preferably formed by a turning operation in a turret lathe which leaves the corners 19 fiat to form straight cutting edges with the arcuate cutting edges 20 therebetween.

In using the invention it is contemplated that a round hole will first be drilled into the sheet of metal M which is to be punched, of a size permitting the rod 13 to extend therethrough, with the die member 10 positioned against one surface of the sheet as shown in FIGURE 4. Thereafter the punch member 12 is fitted onto the rod 13 with its key 12' in the keyway 13" so as to align the punch member with the die. The nut 16 is then placed in position. The ram R is shown as having a cylinder 30 in which a piston 31 is reciprocally supported and has a tubular extension 31' which is suitably screw threaded and attached to the left-hand end of the rod 13. A coil spring 32 is positioned between the piston 31 and a cupshaped cover member 33 which is retained in the cylinder by a ring 34 so that normally the piston 31 is at the righthand end of the cylinder as shown in FIGURE 4.

With the punch and die member assembled in position on a metal sheet M as shown in FIGURE 4, supplying fluid under pressure from a suitable source (not shown) to the conduit 35 which communicates with the right-hand end of the cylinder 30, causes the piston 31 to move toward the left and draw the rod 13 and the attached punch member 12 toward the left to punch a hole in the sheet. With the die shaped as shown, the corners of the punched-out piece of metal are curved in a manner which follows the shape 20 of the cutting edge of the die, with the result that the corners of the punched-out piece do not tend to bind in the die. The central portions of the sides of the square punched-out piece, as they move into the die member, pass through the die member along the recesses 22 so that these portions of the punched-out part do not bind in the die.

I claim:

1. A metal punch and die set comprising, a die member having a square hole therethrough and shallow arcuate grooves in the central portion of each flat side of the hole from a point adjacent the cutting edge to the opposite surface thereof, a backing member fitting against the said opposite surface of the die member having a central cylindrical portion fitting into said arcuate grooves and a larger flat portion fitting against the die member, and a square punch element having flat exterior sides and shaped on its face adjacent the die element to form cutting edges which are flat at the corners and arcuate therebetween.

2. A punch and die of the draw type comprising, a punch and die set as defined in claim 1, a draw rod extending through central bores in the die member and back-up member, and means for securing the die member in fixed position on said rod.

References Cited by the Examiner UNITED STATES PATENTS 7/1929 Doherty et a1. 3036O 3/1953 Nischan 30*360 9/1958 Hempel 7610'7 2/1959 Smith 76-10 7 4 FOREIGN PATENTS 851,760 10/1939 France.

WILLIAM FELDMAN, Primary Examiner.

JAMES L. JONES, JR., Examiner. 

1. A METAL PUNCH AND DIE SET COMPRISING, A DIE MEMBER HAVING A SQUARE HOLE THERETHROUGH AND SHALLOW ARCUATE GROOVES IN THE CENTRAL PORTION OF EACH FLAT SIDE OF THE HOLE FROM A POINT ADJACENT THE CUTTING EDGE TO THE OPPOSITE SURFACE THEREOF, A BACKING MEMBER FITTING AGAINST THE SAID OPPOSITE SURFACE OF THE DIE MEMBER HAVING A CENTRAL CYCLINDRICAL PORTION FITTING INTO SAID ARCUATE GROOVES AND A LARGER FLAT PORTION FITTING AGAINST THE DIE MEMBER, AND A SQUARE PUNCH ELEMENT HAVING FLAT EXTERIOR SIDES AND SHAPED ON ITS FACE ADJACENT THE DIE ELEMENT TO FORM CUTTING EDGES WHICH ARE FLAT AT THE CORNERS AND ARCUATE THEREBETWEEN. 